"There seems to be some correlation between an ability to recognize oneself in a mirror and higher forms of social complexity," said Joshua Plotnik, a graduate student in psychology at Emory University in Atlanta, Georgia.

To assess elephants' self-awareness, Plotnik and his colleagues tested three adult female Asian elephants in front of a mirror.

All three pachyderms sized up their mirror images by inspecting behind the mirror, rubbing their trunks the length of the mirror, or probing their mouths with their trunks to see if their reflections did the same.

One elephant named Happy also passed the so-called mark test, repeatedly touching her trunk to a white X painted on her forehead that was only visible in the mirror.

The researchers say this is firm evidence of mirror self-recognition.

"It's very possible the other two failing [the mark test] was due to issues with the mark itselfperhaps they didn't care about it or weren't interested in it," Plotnik said.

"What we find most important is [that] one passed. That demonstrates elephants have the capacity for this particular form of self-recognition," he continued.

Plotnik and colleagues report their findings today in the early online edition of the current issue of the Proceedings of the National Academy of Sciences.

Big Mirror

Plotnik and colleagues note that elephants failed a previously published test for mirror self-recognition, but they add that the test used a relatively small mirror that was kept out of reach from the elephants.